Ring-in-Ring Assembly Facilitates the Synthesis of a Cyclopara-phenylene Hetero[3]Catenane

Cycloparaphenylenes (CPPs) represent a significant challenge for the synthesis of mechanically interlocked architectures, because they lack heteroatoms, which precludes traditional active and passive template methods. To circumvent this problem and explore the fundamental and functional properties of CPP rotaxanes and catenanes, researches have resorted to unusual non-covalent and even to labor-intensive covalent template approaches. Herein, we report a ring-in-ring non-covalent template strategy that makes use of the surprisingly strong non-covalent inclusion of crown ethers into suitably sized CPPs. By threading a secondary ammonium salt through the crown ether and closing the third ring via Cu-AAC click reaction, we obtained a hetero-[3]catenane comprising [12]CPP, 24-crown-8 and a dibenzylammonium macrocycle. X-ray crystallography shed light on the ring-in-ring pre-organization and the [3]catenane topology was confirmed by NMR and MS-MS studies. Molecular simulations provided insights into the intriguing ring-vs.-ring-vs.-ring dynamics of the [3]catenane, which are highly dependent on the protonation state of the dibenzylammonium site. This ring-in-ring assembly strategy opens new avenues for the synthesis of complex CPP architectures and their use in functional supramolecular systems.